The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
An internal combustion engine generates drive torque by combusting an air and fuel mixture within cylinders. More specifically, air is drawn into the engine and is distributed to the cylinders. The air is mixed with fuel to form a combustion mixture having a desired air to fuel ratio, which is combusted within a cylinder. The combustion process reciprocally drives a piston within the cylinder, which rotatably drives a crankshaft to provide the drive torque.
More recently, alternative fuels, such as alcohol-based fuels, have been developed for use with engine systems. Alcohol-based fuels include methanol and ethanol, for example. Modern engine systems are able to operate using gasoline, alcohol-based fuel or any mixture thereof. However, engine operation must be modified when operating on different fuels because of the different characteristics of each fuel. For example, an engine operating using ethanol or an ethanol and gasoline blend, for example E85 (i.e., a blend of 85% ethanol and 15% gasoline) requires an increased amount of ethanol relative to gasoline at stoichiometry due to different chemical compositions.
Some engine systems include a direct measurement of the ethanol content using a fuel sensor. The implementation of such a fuel sensor increases overall cost and complexity of the engine system.
Other engine systems include an indirect measure of ethanol content. More specifically, an air to fuel ratio calculation is used to determine the ethanol/gasoline fuel content. This is achieved by comparing the mass air flow (MAF) with the predetermined injected fuel quantity at a stoichiometric exhaust condition to provide the air to fuel ratio. The air to fuel ratio is used to determine the fuel content with good accuracy knowing that a stoichiometric air to fuel ratio for ethanol is near 9:1, while gasoline requires an air to fuel ratio near 14.5:1.
While the current state-of-the-art virtual sensor can provide an accurate measurement of fuel content, it is slow and prone to false readings due to the effects of several unrelated engine operating conditions.